The present invention generally relates to a resin-sealed semiconductor device in which a die pad portion having a semiconductor element mounted thereon is exposed from a sealing resin, and a manufacturing method thereof. More particularly, the present invention relates to a resin-sealed semiconductor device preventing generation of resin voids within a sealing resin, and a manufacturing method thereof.
Recent reduction in size of electronic equipments requires high-density packaging of semiconductor components such as a resin-sealed semiconductor device. In response to such a requirement, the semiconductor components are increasingly reduced in size and thickness. In addition to such a trend, semiconductor devices having an increased number of pins are increasingly produced. Accordingly, there is a demand for a small, thin, high-density resin-sealed semiconductor device.
Hereinafter, a conventional resin-sealed semiconductor device having a die pad portion exposed from a resin will be described. FIGS. 11A to 11C show a conventional resin-sealed semiconductor device. FIG. 11A is a plan view, FIG. 11B is a bottom view, and FIG. 11C is a cross-sectional view taken along line A-A1 in FIG. 11B.
As shown in FIGS. 11A to 11C, a semiconductor element 102 is mounted on a die pad portion 101 of a lead frame. The semiconductor element 102 is electrically connected to inner lead portions 103 by thin metal wires 104. The semiconductor element 102 on the die pad portion 101 and the inner lead portions 103 are sealed with a sealing resin 105. The side surface of the sealing resin 105 is flush with the terminal ends of the inner lead portions 103. The bottom surface of the die pad portion 101 is exposed from the sealing resin 105. The tips of the inner lead portions 103 are exposed as external terminals 106.
Hereinafter, a method for manufacturing the conventional resin-sealed semiconductor device will be described. FIGS. 12A to 12D are cross-sectional views illustrating the steps of the method for manufacturing the conventional resin-sealed semiconductor device using a lead frame.
As shown in FIG. 12A, a lead frame is first prepared. The lead frame has a frame portion, a rectangular die pad portion 101 provided within the frame portion, for mounting a semiconductor element thereon, suspended lead portions for supporting the die pad portion 101, and beam-like inner lead portions 103 to be electrically connected to the semiconductor element mounted on the die pad portion 101 by connecting means such as thin metal wires.
As shown in FIG. 12B, a semiconductor element 102 is then bonded to the die pad portion 101 of the lead frame by an adhesive such as silver paste (die bonding step).
As shown in FIG. 12C, electrode pads (not shown) on the surface of the semiconductor device 102 mounted on the die pad portion 101 are respectively connected with the tips of the inner lead portions 103 of the lead frame by thin metal wires 104 (wire bonding step).
As shown in FIG. 12D, with a sealing sheet in close contact with the lead frame, the die pad portion 101, the semiconductor element 102 and the inner lead portions 103 are sealed with a sealing resin 105. In the illustrated example, the sealing step is conducted with the sealing sheet in close contact with the bottom surface of the lead frame. Therefore, the die pad portion 101, the suspended lead portions, the semiconductor element 102, the inner lead portions 103 and the connection regions of the thin metal wires 104 are sealed except the bottom surface of the die pad portion 101 and the bottom surface of each inner lead portion 103. As a result, the bottom surface of the die pad portion 101 is exposed from the bottom surface of the sealing resin 105.
In the conventional resin-sealed semiconductor device and the manufacturing method thereof, a semiconductor element is first mounted on a lead frame and electrical connection thereof is then conducted using thin metal wires. The subsequent resin sealing step is conducted with a sealing sheet in close contact with the bottom surface of the lead frame. In the resin sealing step, however, the air may be introduced into the interface between the sealing sheet and the die pad portion and the inner lead portions of the lead frame. In this case, this air is trapped at the interface without being forced to air vents formed in a mold. As a result, the air is trapped at the end of the die pad, whereby resin voids are generated in the sealing resin near the die pad portion. Recently, such a phenomenon often occurs in the resin sealing step using both a multi-pin, high-density lead frame having leads arranged at smaller intervals and a sealing sheet. This is extremely problematic in manufacturing a resin-sealed semiconductor device having a die pad portion exposed from a resin.
Resin voids thus produced in the sealing resin would generate cracks within the resin during operation in the heating environment, hindering mounting of the resin-sealed semiconductor device on a circuit board. This is not preferable in terms of reliability.
The present invention is made to solve the above conventional problems, and it is an object of the present invention to provide a resin-sealed semiconductor device having a die pad portion exposed from a sealing resin and a manufacturing method thereof, which prevent generation of resin voids within a sealing resin.
According to one aspect of the present invention, a resin-sealed semiconductor device includes a die pad portion for mounting a semiconductor element thereon, a semiconductor element mounted on the die pad portion and having electrodes, a plurality of lead portions arranged with their respective tips facing the die pad portion, thin metal wires for connecting the electrodes of the semiconductor element to the lead portions, and a sealing resin for sealing the die pad portion, the semiconductor element, the lead portions and connection regions of the thin metal wires except a bottom surface of the die pad portion and respective bottom surfaces and terminal ends of the lead portions. The terminal ends of the lead portions are approximately flush with a side surface of the sealing resin. The die pad portion has a first recess formed in an outer periphery of the bottom surface thereof.
Preferably, the resin-sealed semiconductor device further includes suspended lead portions for supporting the die pad portion.
Preferably, the die pad portion has an upward projecting support portion for supporting the semiconductor element. A second recess is provided at a region of the bottom surface of the die pad portion that corresponds to the support portion. The first recess formed at the bottom surface of the die pad portion is a groove-like recess extending from an outer end of the bottom surface of the die pad portion to the second recess.
Preferably, at least the lead portions include first lead portions arranged with their respective tips facing the die pad portion, and second lead portions extending so that their respective tips are located at a position closer to the die pad portion than are the tips of the first lead portions.
Preferably, respective bottom surfaces of the first lead portions and respective bottom surfaces of the second lead portions form land electrodes. The land electrodes are arranged in at least two rows in a bottom surface region of the sealing resin when viewed two-dimensionally.
According to another aspect of the present invention, a method for manufacturing a resin-sealed semiconductor device includes the steps of: preparing a lead frame having a die pad portion provided within a frame portion formed from a metal plate, for mounting a semiconductor element thereon, a plurality of lead portions arranged with their respective tips facing the die pad portion and their respective terminal ends connected to the frame portion, and a sealing sheet attached in close contact with respective bottom surfaces of the lead portions and a bottom surface of the die pad portion, the die pad portion having a first recess formed in an outer periphery of the bottom surface thereof; mounting a semiconductor element having electrodes on the die pad portion of the prepared lead frame with a main surface of the semiconductor element facing upward; connecting the electrodes of the semiconductor element thus mounted on the die pad portion to the lead portions of the lead frame by thin metal wires; and sealing an upper side of the lead frame with a sealing resin so that the die pad portion, the semiconductor element, the lead portions and connection regions of the thin metal wires are sealed except the bottom surface of the die pad portion and the respective bottom surfaces of the lead portions.
Preferably, in the resin sealing step, air trapped between the sealing sheet and the die pad portion of the lead frame is released into the first recess formed at the bottom surface of the die pad portion.
Preferably, after the resin sealing step, the terminal ends of the lead portions are cut away so that the resultant terminal ends of the lead portions are approximately flush with a side surface of the sealing resin.
According to still another aspect of the present invention, a method for manufacturing a resin-sealed semiconductor device includes the steps of: preparing a lead frame having a die pad portion provided within a frame portion formed from a metal plate, for mounting a semiconductor element thereon, suspended lead portions supporting an outer periphery of the die pad portion with their respective tips and connected to the frame portion at their respective terminal ends, and a plurality of lead portions arranged with their respective tips facing the die pad portion and their respective terminal ends connected to the frame portion, the die pad portion having a first recess formed in an outer periphery of a bottom surface thereof; mounting a semiconductor element having electrodes on the die pad portion of the prepared lead frame with a main surface of the semiconductor element facing upward; connecting the electrodes of the semiconductor element thus mounted on the die pad portion to the lead portions of the lead frame by thin metal wires; and attaching a sealing sheet in close contact with at least respective bottom surfaces of the lead portions and the bottom surface of the die pad portion out of a bottom surface of the lead frame, and sealing an upper side of the lead frame with a sealing resin so that the die pad portion, the suspended lead portions, the semiconductor element, the lead portions and connection regions of the thin metal wires are sealed except the bottom surface of the die pad portion and the respective bottom surfaces of the lead portions.
Preferably, after the resin sealing step, the respective terminal ends of the suspended lead portions and the lead portions are cut away so that the resultant terminal ends of the suspended lead portions and the lead portions are approximately flush with a side surface of the sealing resin.
As described above, in the resin-sealed semiconductor device of the present invention, the die pad portion has a first recess formed in the outer periphery of the bottom surface thereof. This structure allows the air (air bubbles) trapped at the interface between the sealing sheet and the die pad portion in the resin sealing step to be released into the first recess or released through the first recess into the second recess formed at the bottom surface of the die pad portion. This prevents the air from remaining at the interface in the resin sealing step, thereby enabling implementation of a void-less resin-sealed semiconductor device. In particular, when the die pad portion has an upward projecting support portion, the air can be released into the second recess under the support portion. This prevents voids from remaining in the sealing resin.
In the manufacturing method of the resin-sealed semiconductor device of the present invention, the resin sealing step is conducted while allowing the air trapped between the sealing sheet and the die pad portion of the lead frame to be released into the first recess formed at the bottom surface of the die pad portion. Generation of resin voids is thus prevented.